Boiler and method for adjusting temperature of steam output from boiler

ABSTRACT

A boiler according to the present invention is a boiler configured to make combustion gas originating from combustion in a burner ( 101 ) flow from a furnace ( 102 ) and pass through a super heater (SH) ( 104 ) and an evaporation tube bank ( 105 ). The boiler includes a downstream shield plate ( 11 A) that is slidable in the vertical direction of the super heater ( 104 ) at a position downstream of the combustion gas flowing above the super heater ( 104 ), thereby regulating the flow rate of combustion gas entering the upper space A of the super heater ( 104 ). By regulating the flow rate of bypass gas ( 12 ) with the downstream shield plate ( 11 A) and in turn regulating the flow rate of mainstream gas ( 13 ), the temperature of steam output from the super heater ( 104 ) is controlled.

TECHNICAL FIELD

The present invention relates to a boiler configured to regulate theamount of combustion gas originating from combustion in a burner andpassing the upper side of a super heater, and to a method for adjustingthe temperature of steam output from such a boiler.

BACKGROUND ART

FIG. 6 is a schematic of an exemplary configuration of a marine boilerhaving a super heater that has been conventionally adopted. Asillustrated in FIG. 6, this conventional boiler 100 includes a burner101, a furnace 102, a front tube bank 103, a super heater (SH) 104, andan evaporation tube bank (rear tube bank) 105. Combustion gas 120originating from combustion in the burner 101 flows from the furnace 102and passes through the front tube bank 103, the super heater 104, andthe evaporation tube bank 105 while exchanging heat therewith. Thecombustion gas 120 flows through an outlet gas duct 106 and then flowsout from a gas outlet 107. The steam collected in a steam drum 108 isthen supplied to some devices (not shown) as a driving source (seePatent Document 1).

In FIG. 6, the numeral 109 indicates a water drum, the numerals 110, 111indicate headers, and the numeral 112 indicates a wall tube.

To control the temperature of the steam generated in the super heater104, the conventional boiler 100 extracts a part of the steam in themidstream of the super heater 104, reduces the temperature of the steamwith the water drum 109, makes the steam exchange heat with the superheater 104 again, and thus adjusts the outlet temperature of the steamgenerated in the super heater 104. Such a method is called a controldesuper heater (CDSH).

For an efficient operation of the boiler 100, the combustion gas 120needs to equally flow through an entire heat exchange tube bank that ismade up of the super heater 104, the evaporation tube bank 105, and thelike. The conventional boiler 100 controls the steam temperature so thatthe boiler 100 is operated efficiently.

[Patent Document 1] Japanese Patent Application Laid-open No.2002-243106

DISCLOSURE OF INVENTION Problem to Be Solved by the Invention

Because the super heater 104 is U-shaped, as illustrated in FIG. 7, whenthe combustion gas 120 bypasses an upper space A on the upper side ofthe super heater 104 as bypass gas 113 without passing the super heater104, the combustion gas 120 flowing in the upper space A does notcontribute to heat absorption of the super heater 104. Therefore, heatexchange with the heat exchange tube bunk made up of the super heater104 and the evaporation tube bank 105 does not take place. This causesproblems of lowering the heat exchange rate in the super heater 104 andshort of steam temperature.

Rated operation may not be available when the steam temperature changesout of a CDSH adjustable range, that is, for example, when the steamtemperature rises to equal to or higher than 560 degrees Celsius or, thesteam temperature is insufficient at, for example, equal to or lowerthan 515 degrees Celsius.

In view of the problems, an object of the present invention is toprovide a boiler configured to regulate flow patterns of combustion gasoriginating from combustion in a burner, adjust the temperature of steamgenerated in a super heater, and enable efficient operation, and amethod for adjusting the temperature of steam output from such a boiler.

Means for Solving Problem

According to an aspect of the present invention, a boiler that flowscombustion gas produced by combustion in a burner through a super heaterand an evaporation tube bank from a furnace, includes: a shield platethat is configured to be slidable in a vertical direction of the superheater or to be rotatable about one end as a rotation axis in order toallow adjustment of an opening degree thereof, the shield plate beingprovided at any one or both of an upstream side and a downstream side ofthe combustion gas flowing above the super heater. A flow rate of thecombustion gas entering an upper space of the super heater is regulated.

Advantageously, in the boiler, a temperature of a part of steamextracted in midstream of the super heater is reduced with a water drum,and the steam is provided to the super heater again, so that atemperature of steam of the super heater is adjusted.

According to another aspect of the present invention, a method foradjusting a temperature of steam of a boiler that flows combustion gasproduced by combustion in a burner through a super heater and anevaporation tube bank from a furnace, includes: providing a shield platethat is configured to be slidable in a vertical direction of the superheater or to be rotatable about one end as a rotation axis in order toallow adjustment of an opening degree thereof, the shield plate beingprovided at any one or both of an upstream side and a downstream side ofthe combustion gas flowing above the super heater; and adjusting a flowrate of the combustion gas entering an upper space of the super heaterby adjusting a sliding degree or the opening degree of the shield plate.

Advantageously, in the method for adjusting a temperature of steam of aboiler, a part of steam is extracted in midstream of the super heater, atemperature of the steam thus extracted is reduced with a water drum,and the steam is provided to the super heater again, so that atemperature of steam of the super heater is adjusted.

Effect of the Invention

According to the present invention, by providing a shield plate that isslidable in the vertical direction of the super heater or that has arotation axis on one end to enable adjustment of its opening degree atany one of a position upstream and downstream or both of the combustiongas flowing above the super heater, the flow patterns of combustion gasoriginating from combustion in the burner can be regulated. The amountof combustion gas that contributes to heat absorption of the superheater can be thus changed. Accordingly, the temperature of steamgenerated in the super heater can be controlled, and a controllabletemperature range can be extended, whereby the boiler can be efficientlyoperated.

The temperature of the steam generated in the super heater can becontrolled by extracting a part of the steam in the midstream of thesuper heater; reducing the temperature of the steam with a water drum;supplying the steam to the super heater again; and thus adjusting thetemperature of the steam in the super heater.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of the configuration of a boiler according to afirst embodiment of the present invention.

FIG. 2 is an illustrative view of flows of bypass gas and mainstream gaspassing through a super heater.

FIG. 3A is an illustrative view of a downstream shield plate whenincorporated in an existing boiler.

FIG. 3B is an illustrative view of a downstream shield plate whenincorporated in a newly manufactured boiler.

FIG. 4 is a schematic of the configuration of the boiler according to asecond embodiment of the present embodiment.

FIG. 5A is an illustrative view of flows of combustion gas in the boileraccording to the first embodiment of the present invention.

FIG. 5B is an illustrative view of flows of combustion gas in the boileraccording to the second embodiment of the present invention.

FIG. 6 is a schematic of an exemplary configuration of a boilerincluding a conventional super heater.

FIG. 7 is an illustrative view of flows of combustion gas in theconventional boiler.

EXPLANATIONS OF LETTERS OR NUMERALS

10A, 10B boiler

11A, 11C downstream shield plate

11B upstream shield plate

12 bypass gas

13 mainstream gas

101 burner

102 furnace

103 front tube bank

104 super heater (SH)

105 evaporation tube bank (rear tube bank)

106 outlet gas duct

107 gas outlet

108 steam drum

109 water drum

110, 111 header

112 wall tube

120 combustion gas

A upper space

H0 total height of the height of the super heater and the upper space

H1, H2 height of the super heater

h1, h2 height of the upper space A

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The present invention will be described in detail with reference to theaccompanying drawings. The embodiments below are not intended to limitthe scope of the present invention. Elements described in theembodiments include their variations readily thought of by those skilledin the art and substantially equivalent elements.

First Embodiment

A boiler according to a first embodiment of the present invention willnow be described with reference to some drawings.

The boiler according to the present embodiment has a similarconfiguration to that of a conventional boiler as shown in FIG. 6;therefore, like elements have like reference numerals, and repeateddescriptions will be omitted.

FIG. 1 is a schematic of the configuration of the boiler according tothe first embodiment of the present invention.

As illustrated in FIG. 1, this boiler 10A according to the presentembodiment is a boiler configured to make combustion gas originatingfrom combustion in the burner 101 flow from the furnace 102 and passthrough the super heater (SH) 104 and the evaporation tube bank 105. Theboiler includes a downstream shield plate 11A that is slidable in thevertical direction of the super heater 104 at a position downstream ofthe combustion gas flowing above the super heater 104, therebyregulating the flow rate of combustion gas entering the upper space A ofthe super heater 104.

Among the whole combustion gas, combustion gas entering the upper spaceA of the super heater 104 is referred to as bypass gas 12 and combustiongas passing through the super heater 104 is referred to as mainstreamgas 13 in the present embodiment.

In the boiler 10A according to the present embodiment, the downstreamshield plate 11A is oriented perpendicular to the flow direction of thecombustion gas. The downstream shield plate 11A provided at a positiondownstream of the combustion gas flowing above the super heater 104 isslidable in the vertical direction. By regulating the flow rate of thebypass gas 12 entering the upper space A of the super heater 104 withthe downstream shield plate 11A, the flow rate of the mainstream gas 13passing through the super heater 104 is in turn regulated.

FIG. 2 is an illustrative view of the flows of the bypass gas and themainstream gas passing through the super heater. As illustrated in FIG.2, by making the downstream shield plate 11A slide in the verticaldirection, the flow rate of the bypass gas 12 can be regulated, and theflow rate of the mainstream gas 13 is in turn regulated.

Specifically, the conventional boiler 100 employs a straightening vane,for example, to regulate the flow of combustion gas and make thecombustion gas flow evenly into the super heater 104 and the evaporationtube bank 105. By contrast, the boiler 10A according to the presentembodiment employs the downstream shield plate 11A that is slidable, andmakes the downstream shield plate 11A slide in the vertical direction,thereby directly regulating the flow rate of the bypass gas 12 enteringthe upper space A of the super heater 104, and in turn regulating theflow rate of the mainstream gas 13 passing through the super heater 104.The temperature of steam generated in the super heater 104 can thus becontrolled.

Specifically, by making the downstream shield plate 11A slide in thevertical direction, regulating the flow rate of the bypass gas 12entering the upper space A of the super heater 104, and in turnregulating the flow rate of the mainstream gas 13, the amount ofcombustion gas that contributes to heat absorption of the super heater104 can be changed. Accordingly, the temperature of steam output fromthe super heater 104 can be controlled.

The downstream shield plate 11A preferably has a height equal to or morethan that of the upper space A of the super heater 104 to enable controlover the bypass gas 12 entering the upper space A with the downstreamshield plate 11A.

In the boiler 10A according to the present embodiment, the downstreamshield plate 11A preferably has a height ranging from 10% to 15%,inclusive, of the total height of the super heater 104 and the upperspace A. More specifically, given that the upper space A isapproximately 15% as high as the total height of the super heater 104and the upper space A, the downstream shield plate 11A shields the upperspace A, whereby the temperature of steam generated in the super heater104 can be controlled by approximately 25%, and further by approximately30%, better than other cases involving no downstream shield plate 11Ashielding the upper space A.

The downstream shield plate 11A may be incorporated in an existingboiler or a newly manufactured boiler, both as the boiler 10A accordingto the present embodiment.

Incorporating the downstream shield plate 11A in an existing boiler thathas been installed enables regulation of the flow rate of the bypass gas12 with the downstream shield plate 11A by a height h1 of the upperspace A relative to a total height H0 of a height H1 of the super heater104 and the upper space A as illustrated in FIG. 3A, whereby the flowrate of the mainstream gas 13 can be regulated.

By contrast, incorporating the downstream shield plate 11A in a newboiler that is newly manufactured makes a height H₂ of the super heater104 smaller than the height H₁ of the super heater 104 in the existingboiler as illustrated in FIG. 3B, thereby increasing a height h2 of theupper space A. This increases the flow rate of the bypass gas 12 that isregulatable with the downstream shield plate 11A in association with theincreased height h2 of the upper space A compared with the existingboiler, thereby in turn increasing the regulatable amount of the flowrate of the mainstream gas 13. Consequently, the fluctuation range ofthe amount of combustion gas that contributes to heat absorption of thesuper heater 104 can be increased, and thus the controllable range ofthe temperature of steam output from the super heater 104 can be madelarge.

In the boiler 10A according to the present embodiment, the height of theupper space A of the super heater 104 may be increased to extend thecontrollable range of the temperature of steam generated in the superheater 104. By increasing the height of the upper space A of the superheater 104 and increasing the slidable range of the downstream shieldplate 11A in the vertical direction, the flow rate of the mainstream gas13 can be regulated, and the controllable range of the temperature ofsteam generated in the super heater 104 can be extended.

Like in a method for controlling the temperature of steam that isemployed with the conventional boiler 100, the boiler 10A according tothe present embodiment may also incorporate a so-called CDSH, whichextracts a part of the steam in the midstream of the super heater 104,reduces the temperature of the steam with the water drum 109, makes thesteam exchange heat with the super heater 104 again, and thus adjuststhe outlet temperature of steam generated in the super heater 104. Byusing the so-called CDSH to control generated steam, as well ascontrolling the flow of combustion gas with the downstream shield plate11A used in the boiler 10A according to the present embodiment andcontrolling the temperature of the steam, the controllable range of thetemperature of steam generated in the super heater 104 can be furtherextended.

Accordingly, with the boiler 10A according to the present embodiment, byregulating the flow rate of the bypass gas 12 entering the upper space Aof the super heater 104 with the downstream shield plate 11A, the flowrate of the mainstream gas 13 passing through the super heater 104 canbe regulated. The amount of combustion gas that contributes to heatabsorption of the super heater 104 can be thus changed, whereby thetemperature of steam generated in the super heater 104 can becontrolled.

Further by increasing the height of the upper space A, the flow rate ofthe bypass gas 12 that is regulatable with the downstream shield plate11A can be increased, and the regulatable amount of the flow rate of themainstream gas 13 is in turn increased. Therefore, the controllablerange of the temperature of steam output from the super heater 104 canbe made large.

Second Embodiment

A boiler according to a second embodiment of the present invention willnow be described with reference to FIG. 4.

FIG. 4 is a schematic of the configuration of the boiler according tothe present embodiment.

The boiler according to the present embodiment has a similarconfiguration to that of the boiler according to the first embodiment;therefore, like elements have like reference numerals, and repeateddescriptions will be omitted.

As illustrated in FIG. 4, this boiler 10B according to the presentembodiment includes an upstream shield plate 11B at a position upstreamof combustion gas flowing above the super heater 104 in the boiler 10Ashown in FIG. 1, and a downstream shield plate 11C replacing thedownstream shield plate 11A at a position downstream of combustion gasflowing above the super heater 104 and having a rotation axis on one endto enable adjustment of its opening degree.

Specifically, the downstream shield plate 11C has a rotation axis on itsupper or lower end to enable adjustment of its opening degree. Referringto FIG. 4, the downstream shield plate 11C has a rotation axis on itslower end to enable adjustment of its opening degree.

The upstream shield plate 11B provided at a position upstream of thecombustion gas flowing above the super heater 104 is slidable in thevertical direction, and the downstream shield plate 11C provided at aposition downstream of the combustion gas flowing on the upper side ofthe super heater 104 has a rotation axis on its lower end to enableadjustment of its opening degree. With this arrangement, the flow rateof the mainstream gas 13 passing through the super heater 104 isregulated.

FIG. 5A is an illustrative view of flows of combustion gas in the boileraccording to the first embodiment of the present invention. FIG. 5B isan illustrative view of flows of combustion gas in the boiler accordingto the second embodiment of the present invention. Referring to FIG. 5B,the downstream shield plate 11C has a rotation axis on its upper end toenable adjustment of its opening degree.

Among the whole combustion gas in the boiler 10A according to the firstembodiment of the present invention, the bypass gas 12 is controlled toflow into the super heater 104 on the downstream of the super heater 104with the downstream shield plate 11A as illustrated in FIG. 5A;therefore, the bypass gas 12 on the upstream of the super heater 104does not contribute to heat absorption. By contrast, in the boiler 10Baccording to the second embodiment of the present invention, by makingthe upstream shield plate 11B slide upward as illustrated in FIG. 5B,the bypass gas 12 can be merged with the mainstream gas 13.

The downstream shield plate 11C when closed can prevent the bypass gas12 or the mainstream gas 13 ascending toward the upper space A of thesuper heater 104 from leaking out of the upper space A of the superheater 104. Accordingly, the flow rate of the mainstream gas 13 can beincreased in ratio. By controlling the flows into the super heater 104on both the upstream and the downstream of the super heater 104, thebypass gas 12 and the mainstream gas 13 can contribute to heatabsorption of the super heater 104 on both the upstream and thedownstream of the super heater 104.

The use of the boiler 10B according to the second embodiment of thepresent invention can thus further extend the controllable range of thetemperature of steam generated in the super heater 104.

By regulating the flow rate of the bypass gas 12 entering the upperspace A of the super heater 104 with the upstream shield plate 11B andthe downstream shield plate 11C, the flow rate of the mainstream gas 13passing through the super heater 104 can be regulated. The amount ofcombustion gas that contributes to heat absorption of the super heater104 can be thus changed, whereby the temperature of steam output fromthe super heater 104 can be controlled.

In the boiler 10B according to the present embodiment, by regulating theflow rate of the bypass gas 12 entering the upper space A of the superheater 104 with the upstream shield plate 11B and the downstream shieldplate 11C, the flow rate of the mainstream gas 13 passing through thesuper heater 104 can be regulated. The amount of combustion gas thatcontributes to heat absorption of the super heater 104 can be thuschanged, whereby the temperature of steam output from the super heater104 can be controlled.

While the boiler 10B according to the present embodiment includes theupstream shield plate 11B and the downstream shield plate 11C above thesuper heater 104, the present invention is not limited thereto. Any oneof the upstream shield plate 11B and the downstream shield plate 11C maybe provided above the super heater 104. Alternatively, the downstreamshield plate 11A employed in the boiler 10A according to the firstembodiment illustrated in FIG. 1 may replace the downstream shield plate11C and be provided above the super heater 104, together with theupstream shield plate 11B. Furthermore, the upstream shield plate 11Bmay be a shield plate having a rotation axis on one end to enableadjustment of its opening degree like the downstream shield plate 11C,whereby the shield plates on both the upstream and the downstream abovethe super heater 104 enable adjustment of their opening degrees.

In the boilers 10A and 10B according to the present invention, bychanging the flow patterns of combustion gas and regulating the flowrate of combustion gas passing through the super heater 104, and thuschanging the amount of combustion gas that contributes to heatabsorption of the super heater 104, the temperature of steam output fromthe super heater 104 can be controlled.

Therefore, they are applicable for marine boilers; however, the presentinvention is not limited thereto.

INDUSTRIAL APPLICABILITY

As described above, the boilers and the methods for adjusting thetemperature of steam output from a boiler according to the presentinvention can regulate the flow rate of combustion gas entering theupper space of a super heater with a shield plate, change the flowpatterns of combustion gas, and regulate the flow rate of combustion gaspassing through the super heater, thereby changing the amount ofcombustion gas that contributes to heat absorption of the super heater.The boilers and the methods, therefore, are suitably applicable forboilers that can control the temperature of steam output from the superheater and for methods for adjusting the temperature of steam outputfrom such boilers.

1. A boiler that flows combustion gas produced by combustion in a burnerthrough a super heater and an evaporation tube bank from a furnace, theboiler comprising: a shield plate that is configured to be slidable in avertical direction of the super heater or to be rotatable about one endas a rotation axis in order to allow adjustment of an opening degreethereof, the shield plate being provided at any one or both of anupstream side and a downstream side of the combustion gas flowing abovethe super heater, wherein a flow rate of the combustion gas entering anupper space of the super heater is regulated.
 2. The boiler according toclaim 1, wherein a temperature of a part of steam extracted in midstreamof the super heater is reduced with a water drum, and the steam isprovided to the super heater again, so that a temperature of steam ofthe super heater is adjusted.
 3. A method for adjusting a temperature ofsteam of a boiler that flows combustion gas produced by combustion in aburner through a super heater and an evaporation tube bank from afurnace, the method comprising: providing a shield plate that isconfigured to be slidable in a vertical direction of the super heater orto be rotatable about one end as a rotation axis in order to allowadjustment of an opening degree thereof, the shield plate being providedat any one or both of an upstream side and a downstream side of thecombustion gas flowing above the super heater; and adjusting a flow rateof the combustion gas entering an upper space of the super heater byadjusting a sliding degree or the opening degree of the shield plate. 4.The method for adjusting a temperature of steam of a boiler according toclaim 3, wherein a part of steam is extracted in midstream of the superheater, a temperature of the steam thus extracted is reduced with awater drum, and the steam is provided to the super heater again, so thata temperature of steam of the super heater is adjusted.